Solvent Extraction of Selenium in Hydrochloric Acid Media by Using Triisobutyl Phosphate and Triisobutyl Phosphate/Dodecanol Mixture

The objective of the present study was to investigate the mechanism of selenium extraction in hydrochloric media by solvent extraction which was carried out in two steps. First, the extraction of selenium by triisobutyl phosphate (TIBP) was employed, and then in the next step, Dodecanol was used as a modifier. The effect of concentration of acid, concentration of TIBP in the organic phase, pH, temperature and modifier on the extraction of selenium(IV) was studied. The results showed that the extraction of selenium by TIBP was not favorable especially in less pH values. But there was a sharp and sudden increase in the extraction of selenium(IV) at the pH around 8–8.5 that was evaluated and proved by comparing the ORP graph of selenium extraction from hydrochloric media with Pourbaix graph of selenium in the hydrochloric media, and FTIR spectra at three points, before, after and at the peak of extraction. Thermodynamic of the process was also studied. The enthalpy of the process was calculated by the plot of log D versus 1/T × 10 −4 and the value of enthalpy was estimated to be equal to −15.4 J/mol which indicated an exothermic reaction. In the next step, the extraction of selenium by TIBP in the presence of Dodecanol as a modifier was surveyed. The result represented that the extraction of selenium increased up to 99 % by using Dodecanol as a modifier at low pH values.